Fire on a CGH2 trailer during filling

Near the end of the process of filling a gaseous hydrogen tube trailer at a liquid hydrogen trans-filling station, a safety pressure-relief device (PRD) rupture disc on one of the tube trailer’s burst and vented hydrogen gas. The PRD vent tube directed gas to the top of the trailer where the hydrogen vented and ignited, blowing a flame straight up in the air.
The operator filling the tube trailer heard a loud explosive sound from the sudden release of hydrogen gas and saw flames immediately. The operator closed the main fill valve on the tube trailer, stopping the hydrogen fill; however, the ten cylinders on the tube trailer were almost full (2500 psig/173 bar).

The facility deluge system was turned on and the emergency responders sprayed the adjacent trailers to prevent escalation. The emergency crews closed the 10 individual tube fill isolation valves located at the rear of the tube trailer and this extinguished the fire. There was no property damage from this event.

The PRD rupture disc designed for 3500 psig (241 bar) failed at about 1000 psig (69 bar) below rated pressure.

The INITIATING CAUSE was the premature failing of the burst disc.

Post-incident examination of the PRD rupture discs lot by the manufacturer found that all of the lot conformed to specification.

According to H2TOOLS report, the ROOT CAUSE was an unexacted premature failure of the burst disk .

burst disc

The hydrogen tube trailer involved in this incident was doing its first fill after requalification, where all the PRDs had just been replaced.

DESCRIPTION of the EQUIPMENT
The trailer consisted in ten tubes with a nominal pressure of 3000 psi (200 bar).
The ten PRDs on the tube trailer (one for each hydrogen tube) are located at the front of the trailer and each PRD has a vent pipe to direct vented hydrogen to a safe location on top of the tube trailer.
The gas transfer station was filling trailers from a liquid hydrogen stationary storage. The tube trailer involved in this incident was one of two tube trailers being filled simultaneously and was second in a line up of five tube trailers parked adjacent to one another at this location.

Only a minor injury: first aid was required for a mechanic working under the tube trailer during the filling process who bumped into the trailer several times during a hurried exit when he heard the loud noise.

Emergency responders were dispatched to the scene and the facility deluge system was turned on. This system is designed to cover the trailer fill aisle with water: it consists of nozzles at the rear of the trailer and a fire cannon directed to the front. When the emergency responders arrived, they immediately began spraying the adjacent trailers to ensure that they stayed cool.
The emergency crews closed the 10 individual tube fill isolation valves located at the rear of the tube trailer and this extinguished the fire. Total time to control the incident was less than 10 minutes and there was no property damage from this event.

All safety systems worked as they should and emergency responders from outside the plant were not needed.
Despite the grounding of the vessels had been done before starting the filling, the hydrogen ignited immediately. This is not uncommon.
The manual operations at the back of the tube trailer, to shut off the hydrogen filling valves could take place because this area was covered by deluge nozzles and located 40 feet (12.2 meters) away from the fire at the affected vent stack.
The plant emergency responders measured a temperature of 300°F (149°C) by means of a thermal reading device. Based on this value, they assumed that the adjacent tube trailers were heating up from the fire. This slightly delayed the closing of the cylinder isolation valves on the tube trailer. Since the post-incident investigation found no paint discoloured or burnt, the temperature taken by the emergency responders was likely near the flaming vent discharge point.

A water cannon belonging to the facility safety deluge water system was a little off target and had to be repositioned and stabilized to ensure that it does not move in the future.